Sprue wire



J. P. BELL SPRUE WIRE Jan. 10, 1933.

Filed Aug. 9,.1932

Patented Jan. 10, 1933 JOHN P. BELL, OF BALTIMORE, MARYLAND SPR'UE WIRE Application filed August 9, 1932.

' This invention is a novel improvement in dental sprues, and the principal objects of the invention are to provide a simple, novel v and etiicient sprue having one or more thin flexible copper wires mounted in a relatively thick tapered base, of brass or the like, for use in removing the wax patterns for gold surface inlays from the cavities in teeth, the thin flexible copper wires being adapted when 0 slightly heated to be inserted into the wax pattern in the cavity without distorting the wax, and when cooled to adhere to the wax with greater strength than the usual phonograph needle now commonly employed by dentists for removing the wax pattern from the cavity; also to provide thin flexible sprue wires which will be capable of ample deflection, or curling over, without in any way injuring the wax pattern, in event the sprue 20 is sufiiciently long to strike the bottom of the cavity while being inserted in the wax; also to provide a thin flexible sprue which will be capable of readily flexing at its junction with thebase whereby if the operator should knock the base when the sprue is in the wax pattern the latter will not be injured, or distorted out of shape, as would i be the case if the wires were shifted laterally in the wax.

Another object of the invention is to provide a novel sprue base, holding one or more sprue wires, the base tapering towards the wires on all sides to permit ready withdrawal of the base from the investment mold used for forming the gold inlay, the base being of relatively thick brass and retaining the heat much longer in the operation of inserting the wires into the wax in the cavity of the tooth; also to provide a sprue base of sufiicient size to permit easy handling of the sprue and greater accuracy when being inserted in the wax pattern; also to provide a sprue base having cupped recesses at the junction of the wires with the base to prevent the Wax from rising onto the base when inserted in the wax filling; and to provide a base for the sprue wires which will readily adapt itself to the ring of the mold used in casting the gold inlay. V

In present day dental practice it is cus- Serial No. 628,102.

tomary for dentists to use a phonograph needle or the like to withdraw the wax pattern used for making the gold inlay from the tooth cavity. Such needles are obviously inflexible, and relatively thick, and comequently when inserted in the wax they distort the pattern out of shape by lumping of wax adjacent the needle, due principally to the large cross-section of the needle. Moreover, when such needles are withdrawn from the wax pattern, the large needle has a tendency to pull the wax adjacent the needle further upwardly or outwardly with the needle thereby further distorting the wax. Hence when the gold inlay is formed from such dis- 55 torted wax pattern the inlay is not accurate and causes considerable trouble in properly conditioning the inlay for the cavity.

When using my novel sprue containing soft flexible copper wires of small constant diameter, the small wires prevent the wax from becoming distorted when inserting or withdrawing the sprue from the wax, and such wires have been found by actual tests to produce greater adhesion in the wax than the phonograph needle due to the small diam eter. Other minor objects of the invention will be heinafter set forth.

I will explain the invention with reference to the accompanying drawing, which illustrates one practical embodiment thereof to enable others to adopt and use the same, and will summarize in the claims the novel features of construction and novel combinations of parts for which protection is desired.

In said drawing:

Fig. 1 is a perspective view of my novel sprue, showing two sprue wires mounted in the base.

Fig. 2 is an end elevation thereof; or of a sprue having a single wire.

Fig. 3 is a side elevation of the sprue shown in Fig. 1.

Fig. 4 is a sectional view showing a tooth with the sprue inserted in the wax pattern in the cavity disposed in the buccal or lingual surface of the tooth, and showing one sprue bent to conform with the cavity.

Figs. 5 and 6 are sectional views showing a sprue with its wire inserted in the wax patterns in cavities disposed in the mesial or lingual surfaces of a tooth.

Fig. 7 is a side elevation of the sprue mount ed in the holder for use in an investment mold.

Fig. 8 is a top plan view of the holder, detached.

Fig. 9 is a section through an investment mold showing the sprue, carrying the wax pattern, and mounted in the holder, and showing one soft wire sprue bent in the wax pattern.

Fi 10 is a section through the investment mold after the holder, sprue, and pattern have been removed, and ready to receive the molten old. g Asshown in Figs. 1-3 the base 1 comprises a.r-snbstantially rectangular body, preferably '01 brass,tapering on all four sides towards the spnue wires 2, said base having projections 11!, on one edge, at opposite ends, into which the sprue wires 2 are fixedly inserted in'qmy'desired manner. T hewires 2 are pref- 'crably of soft flexible copper, and are of small constant diameter. The ends of the projeeflions 10.-of the base at the points of junction With the wires 2 are preferably cupped as at 11). The flexibility of the wires 2 gives the operator a chance to adjust the sprue wires at. their junctions with the base 1, the wires 2 of the sprue being inserted into the wax patternuntil the concave ends 1?) of the sprue body come into contact with the wax pattenn. Heated wax will'travel up the soft wire'2 until it enters the concave ends 1?) of the-spline body, and hence the concave ends will receivev a small portion of heated wax forced up: around the soft wires 2 by the insertion of the soft wire into the wax. The

concave ends 1?; of the sprue body only come in contact with wax pattern, and are not forced into the wax pattern. This prevents the wax fromlloodingaround sprue body and distorting the preformed wax pattern. By actual tests it has been found that my soft copper sprue wires have much greater retaining strength than the phonograph needles now used, the adhesion of the wax to the small copper wire being about five timesas'great as the adhesion of the wax to a phonograph needle. In Figs. 1 and 3 the sprue is shown as having two wires 2 and is adapted for removing one large wax pattern havingone or more surfaces, while in Fig. 2 a single wire 2 is shown, this sprue being adapted for extracting simple or small wax patterns.

Fig. 4 shows the sprue wires 2 inserted in the wax pattern in a cavity in the buccal or lingual surface of the tooth T, showing one soft copper wire 2 deflected by striking tho-bottom of the cavity and, in following the lineof least resistance, curling as at 2a in the wax. Thesoft wires 2 when inserted into the waxpatterns \V may come into contact with irregular surfaces of the tooth cavity and will follow the line of least resistance and may be deflected to either side of such 0bstruction without injuring the wax pattern.

In Fig. 5 the single sprue wire 2 is shown inserted in a. wax pattern W in a cavity in a mesial or distal surface of a tooth T. The soft wire sprue 2 is sufiiciently flexihleto permit the base 1 to be rocked to either .side (as shown in dotted lines) while the wire 2 is in the wax without distorting the pattern W, such motion being made possible by the attachment of the small flexible wire 2 to the thicker base 1, the wire 2 bending at its junction with the base 1 above the wax. This rocking motion may be unintentional and caused by normal handling of the sprue by the dentist when removing the wax pattern from the cavity of the tooth. Hence in using my novel sprue the operator need not be is careful as when using thestifli' phonograph needle, which necessitates the exercise of great care in order to prevent rocking of the needle in'the wax.

In Fig. 6 the single sprue wire 2 is shown inserted in a wax pattern W2 lying on the lingual surface of an incisor tooth T2. In this case the soft wire 2 inserted in the wax also follows the line of least resistance, and is deflected by the bottom of the'cavity.

My novel sprue is particularly adapted fur use with a holder 3 (Figs. 7 and 8) forming part of an investment mold as'shown' in Fig. 9. The. holder 3 is preferably semi-globular and provided with a rectangular recess 3a; for receiving the base 1 ,of the sprue as in Fig. 7 which may be held therein by means of wax 3b (Fig. 7) or the like. When the holder 3 with the'sprue 1 carrying the wax pattern Wis placed in the investment mold'M as shown in Fig. 8. and the investment 1111- terial poured therein around the sprueand wax pattern, and after the investment material has set, the holder 3 and sprue/1' may be readily withdrawn by slightly heating the mold M: and, upon further heating, the'wax of the/pattern W in the mold M may also be withdrawn leaving a cavity M2 in the mold as shown in Fig. 9. If a sprue wire 2 is bent as shown in Fig. 9. upon heating the mold the sprue may be forced to straighten out against the wall of the investing material. The cavity M in the moldM left by removing sprue 1 is so shaped that it allows a. greater amount of gold to enter the inlay mold M2, left by the wax pattern W, as compared with the needle methods now in use.

Use of my novel sprue and holder results in less'failures in making gold inlays due-to the larger opening M in the mold left by the sprue 1, giving the gold a better chance thin flexible sprue wire mounted in the smaller end of said base.

2. A dental sprue, comprising a base tapering in thickness towards one end; and a thin flexible sprue wire mounted in the smaller end of the base; the end of the base at the junction of the wire being cupped.

3. A dental sprue, comprising a base having spaced projections at one end; and thin flexible sprue wires mounted in and extending from said projections.

4. A dental sprue, comprising a base having spaced projections at one end; and thin flexible sprue wires mounted in and extending from said projections; the outer ends of the projections at the junctions of the wires being cupped.

5. A dental sprue, comprising a base hav ing spaced projections along one end, said base tapering in thickness towards said proj ections; and thin flexible sprue wires mounted in and extending from said projections.

6. A dental sprue, comprising a base hav ing spaced projections along one end, said base tapering in thickness towards said projections; and thin flexible sprue wires mounted in and extending from said projections; the outer ends of the projections at the junctions of the wires being cupped.

JOHN P. BELL. 

